Catalyst for manufacture of methacrylaldehyde

ABSTRACT

CATALYSTS WHICH ARE USEFUL FOR VAPOR PHASE OXIDATION OF ISOBUTYLENE, CONSISTING OF INTIMATELY MIXED OXIDES OF COPPER, MOLYBDENUM AND TELLURIUM ON A REFRACTORY SOLID SUPPORT ARE MADE, FOR EXAMPLE, BY COATING A SOLID SUCH AS SILICON CARBIDE WITH AN AQUEOUS SOLUTION OF COPPER, MOLYBDENUM AND TELLURIUM COMPOUNDS AND HEATING THE COATED SOLID TO AT LEAST 350*C.

United States Patent O U.S. Cl. 252-437 2 Claims ABSTRACT OF THEDISCLOSURE DESCRIPTION OF THE INVENTION This application is a divisionof U.S. Ser. No. 528,050, filed Feb. 17, 1966, now U.S. Pat. 3,439,045,which in turn is a continuation-in-part of U.S. patent application Ser.No. 208,637, filed July 9, 1962, now abandoned and U.S. Ser. No. 247,267now abandoned, Ser. No. 247,268, now abandoned and Ser. No. 247,307, nowabandoned,

' the latter three applications having been filed on Dec. 26,

The present invention is directed to the oxidation of 2-methylpropene(isobutylene) to methaqrylaldehyde (methacrolein) with maximumselectivity and catalyst life, with minimum expense for catalystreplacement and without the necessity of using purified isobutylene asraw material.

In US. Ser. No. 208,637 the applicants disclosed the oxidation ofisobutylene by contacting a gaseous feed stream consisting ofisobutylene, air and' steam with a novel metal oxide catalyst complex,for example, a composition having the empirical formula Cu Teg,f PMo Osupported on lumps of cemented silicon carbide aggregate. The use of acatalyst composition having the empirical formula Cu Te Mo O is alsospecificallyiexemplified in the application to demonstrate theeffectiveness of simple compositions based only on the metal6xides which"ice composition produced by heating an intimate mixture consistingessentially of oxides of copper, molybdenum and tellurium to atemperature at least as high as that employed in converting isobutyleneto methacrolein, said oxides being present in a ratio of about 1 to 20moles of copper oxide and at least 0.01 mole of tellurium oxide per 12moles of molybdenum oxide, said metal oxide composition being on thesurface of a refractory solid which is essentially non-reactive withrespect to the metal oxide composition and possesses a surface area ofless than about 10 sq. meters per gram.

So that the process may be better understood, there is presented below adetailed discussion with illustrative examples.

(A) THE CATALYST Before operating the process, it is necessary to obtaina quantity of the catalyst, which is of an unusual type, possessing someunique characteristics. The selection of the particular metal oxidecomposition for the purpose is based on its ability to convertisobutylene to methacrolein with selectivities as high as to percent,even when conversion rates are maintained above about 65 percent byregulation of temperature and oxygen concentration. The preferred metaloxide compositions are capable of extraordinarily high yields ofmethacrolein per pound of active catalyst. Consequently, smalldifferences in the price of the catalyst raw materials have no greateconomic significance, unless they directly aifect the useful life orthe overall activity of the catalyst. The selection of raw materials forcatalyst manufacture is therefore based main- 1y on these factors, aswell as convenience.

(1) Catalyst carrier or support The catalyst support is selected fordurability and enhancement of catalyst activity and life. Siliconcarbide aggregate consisting of crystals of silicon carbide cementedtogether to form porous masses has been found to possess the bestcombination of properties. However, other refractory solids which arenon-reactive with respect tothe metal oxide composition such as, forexample, alumina arid zirconium silicate can be employed, providing theyhave a surface area of less than about 10 sq. meters per gram andpreferably less than 5 sq. meters per gram. The

size and shape of particles of catalyst support are selected so as tominimize packing, clogging and formation of large cavities in thecatalyst bed.

(2) Catalyst composition The catalyst composition which is coated on thesupport is of the metal oxide type, consisting of a complex systemresulting from interaction of oxides of copper, molybdenum andtellurium. A suitable composition can be prepared, for example, byforming an intimate mixture of these oxides in the proportions indicatedbelow, followed by interaction at elevated temperature:

Moles CuO a 1-20 Te0 0.01-10 MoO u 12 The empirical formula of thecatalyst may vary over rather broad limits, as indicated by the aboveranges of proportions. Although the composition of the catalyticallyactive sites in such a composition may have a specific empiricalformula, this would be difiicult to prove. Efforts to discover the rangeof empirical formula of a catalyst possessing optimum activity andselectivity have established preferred limits of composition of aspecific interaction product as indicated below:

The oxygen content of the composition exhibits some variability and isdifiicult to determine accurately. Since metal oxides in general arenon-stoichiometric compositions, some variability in the oxygen analysisis not unusual. An intimate mixture of metal oxides may conceivably bemade by grinding or mulling followed by heating. However, the preferredmethod of manufacture is to prepare an aqueous solution of water-solublecompounds of copper, tellurium and molybdenum, coat the solution on acarrier, evaporate the water and then heat the dried solid material. Inthe preferred method of catalyst manufacture, differential thermalanalysis indicates that at least one reaction occurs at temperaturessubstantially lower than the temperatures at which the isobutyleneoxidation process is customarily operated. For instance, inmanufacturing the composition set forth above by empirical formula, thedried coating of soluble salts appears to undergo reactions within therange of about 115 to 175 C. to yield a product of apparently stablecomposition. For want of a better descriptive term this product iscalled an intimate mixture of metal oxides. Although the best performingproduct has a rather definite empirical formula and is obtained by meansof a chemical reaction, it is very difficult to characterize. Theprofuseness of peaks obtained by X-ray diffraction appears to indicatean extremely complex molecular or crystalline structure (a very largenumber of ordered spatial arrangements of atoms). Occasionally a sampleof this intimate mixture of metal oxides gives indication of undergoinganother reaction at about 350 C., which is apparently irreversibleduring the normal useful life of the substance as a catalyst.

For the sake of convenience in producing an adherent coating of uniformcomposition on the catalyst support, it is preferred to employwater-soluble metal salts in homogeneous solution. Preferably, these aresalts such as nitrates, phosphomolybdates, silicomolybdates, telluratesand ammonia complexes, which decompose very readily to form an intimatemixture of metal oxides. If true homogeneous solutions are not readilyobtainable with materials at hand, undissolved components may beincorporated as dispersed or suspended particles with satisfactoryresults.

Following is a suitable procedure for preparation of the preferred typeof catalyst:

A hot solution of 10.9 g. of Cu(NO -3H O, 1.3 g. of telluric acid and11.7 g. of phosphomolybdic acid in 50 ml. of water is added withstirring to 328 g. of a silicon carbide aggregate having an 8 to 12 meshsize. The addition is carried on in such a manner that the evaporationof the water and nitrogen oxide evolution are very rapid. The resultingdry particles of catalyst are fired in an oven for two hours at 1000 F.The dried catalyst is obtained in a yield of 341 g. The empiricalformula of the catalyst is Cu Te PMo O (empirical formulas givendetermined by calculation). The effectiveness of the catalystcomposition in carrying out the process is demonstrated as follows:

A portion of the catalyst (200 ml.) is placed into a 400-ml. oxidationreactor. A feed stream vapor of isobutylene is employed having thefollowing composition by volume: isobutylene-10.3%; air51.5%; and water38.2%. The reaction is conducted at approximately atmospheric pressureemploying a temperature of 476 C. The contact time of the gaseous feedwith the catalyst bed is an average of 1.8 seconds. The product isrecovered in the customary manner employing water scrubbers and is 4analyzed by the Orsat and GLC methods (as used herein, GLC means gasliquid chromatography). The conversion of isobutylene is 33 percent andthe yield of methacrolein is 69 percent.

The following aqueous mixture is also advantageously employed in thepreparation of a catalyst by the procedure exemplified above: 11.6 g. ofsilicomolybdic acid, 5 ml. of nitric acid, 13 g. of Cu(NO -3H O, 1.3 g.of telluric acid and 75 ml. of water. The mixture is added to 328 g. ofa 4-6 mesh of silicon carbide aggregate having a surface area of lessthan about 5 meters per gram. The weight of the fired catalystcontaining 4.1 percent by weight of the complex, ready for use in theoxidation process, is 342 g. Empirical formula:

A ZOO-ml. portion of the catalyst is charged into the conventionaloxidation reactor employed in the procedure exemplified above. Theheated catalyst bed is contacted with a mixed vapor feed stream havingthe following composition by volume: isobutylene-16.2%; air- 69.5%; andsteam14.3%. The reaction is conducted at approximately atmosphericpressure at an average temperature of 507 C. The apparent contact timeis 2.5 seconds. The reaction products are analyzed by the Orsat and GLCmethods. A 46 percent conversion of the fed isobutylene is obtained witha methacrolein yield of 73 percent.

Water solubility of reactants was obtained by the use of phosphomolybdicand silicomolybdic acids in the above procedures. However, solubility ofreactants may be achieved conveniently by other means as shown in theequation and procedure below:

The 13.82 g. (0.096 mole) sample of M00 dissolved exothermally in 50 ml.NH OH (2830% NH The 17.40 g. (0.072 mole) sample of copper nitrate wasalso dissolved in 50 ml. of NH OH. The ammonium hydroxide solutions weremixed and a clear blue solution resulted. Phosphoric acid (85 percent)(0.92 g., 0.008 mole) was added with no precipitation. Telluric acid(2.76 g., 0.012 mole) was dissolved in water and added dropwise to thewell stirred ammonia solution. This latter addition caused someturbidity but precipitation was not noted over a short period of time.The solution was added to 183 g. (about 218 cc.) of 4-6 mesh CMMCarborundurn" in a heated dish. The coating and firing procedure werecarried out in the usual maner. The fired catalyst had a very uniformcoating of catalyst composition. The catalyst weighed 204.5 g.,calculated as 10.5 percent Cu Te PMo O on porous SiC.

A double-coated catalyst having a physical structure which is especiallydurable and long-lived may be made by the following procedure;

Copper nitrate trihydrate (7.25 g., 0.03 mole) and telluric acid (2.30g., 0.01 mole) were dissolved in 45 ml. of water and added to 240 g. of46 mesh CMC Carborundum in a Vycor dish. The catalyst solution wasabsorbed by the carrier at ambient temperature. After partial drying.the coated carrier was fired for two hours at 1000 F. The sample nowweighed 244 g. and theoretically contained 1.6 percent Cu TeO on CMCcarrier. The initial coated catalyst was then treated with 45 ml. of anaqueous solution containing 10.87 g. (0.045 mole) copper nitratetrihydrate and 0.0005 mole equivalent soluble tellurophosphomolybdate(ratios:

The completed catalyst was again fired and weighed 258 g. Thepreparation was repeated employing CMM Carborundum. l

The catalyst prepared as described above on CMC carrier was evaluated ina conventional oxidation reactor. With a feed gas stream in the molarproportions of 1 isobutylene, 1.5 oxygen (as air) and 2.1 water, thecatalyst converted 48 percent of the isobutylene at 492 C. to yield 75percent methacrolein. Evaluation of the catalyst prepared on the CMMcarrier under similar oxidation conditions indicated 57 percentisobutylene conversion with a 74 percent yield of methacrolein.

The double coated catalysts were stacked in a single tubular reactor andthe layers were separated by silicon carbide. Normal oxidationconditions to include Water, air and isobutylene were maintained for aperiod of 1000 hours. The catalysts were separated and again evaluatedin an analytical oxidation reactor. The yields and conversions had notchanged, substantially, over the 1000 hour period. The analysesindicated good catalyst stability on both carriers (CMM and CMCCarborundum).

If desired, catalyst life can also be prolonged by the procedureillustrated below:

Considerable tellurium is lost with time from the isobutylene oxidationcatalyst. This loss of tellurium may be attributed to decomposition ofthe catalyst with the sublimation of tellurium oxide, since it sublimesat 450 C.; however, the exact mechanism of loss is not known. This lossof tellurium may become a serious problem, resulting in a decline ofselectivity after 2000 hours or more, so that replacement of thecatalyst becomes necessary.

The loss of tellurium from the oxidation catalyst may be prevented bythe addition of tellurium oxide vapor to the feed of the reactor.Studies with a catalyst on a Carborundum CMM support and with telluriumoxide in the feed have shown that the catalyst loses little or notellurium after 1000 hours. Furthermore, the activity and selectivity ofthe original catalyst have been maintained. This information issummarized in' the table below.

cooled catalyst weighed 433 g. The calculated stoichiometry approximated5% Cu Te PSn Mo O on CMM carrier. The catalyst indicated enhancedactivity. Comparative data verifying the effects of tin are shown below.In order to obtain a valid comparison, the added tin compound wasreacted with portions of a single batch of supported catalyst andcomparisons were made with other portions to which no tin was added.Although some improvement is noticeable in conversion of pureisobutylene, the greatest benefit is evident in conversion of theisobutylene in the butane-butene mixture.

FEED.PURIFIED ISOBUTYLENE 7.5 C11 T91.5P1\I012O50.5 CD11 Percent Isobu-Percent Contact Feed Mole tylene yield time, Ratio 0011- methasecondsI04-Og-Hg0 verted crolein Temperature C.:

7.5 Cu Te1.aPMo12O50.s+ 0.2 SHOP-(TRIM FEED-49 ISOBUTYLENE ASBU'lANE-BUTENE MIXTURE 7.5 Cu Te1.5Pl\ .(012O50.s.Cl\IC 7.5CllgTBLsPMOmOsds-l- 0.3 S1102-CMM One problem associated withisobutylene oxidation is the formation of tar-like, non-volatileby-products which may deposit in the catalyst bed, on the walls ofreactors TABLE I.--1,000 HOUR CATALYST LIFE STUDIES Although along-lived, very active and selective catar quenching the hot gases asthey leave the reactor. Both lyst is probably the most economical in thelong run, the following procedure is recommended for production ofcatalyst at the lowest initial cost per unit weight of active metaloxide composition:

The following reagents were added to a 1000 ml. flask fitted with amagnetic stirrer, heating mantle and reflux condenser: 27.64 g. (0.192mole) of M00 2.00 g. (0.017 mole) of 85 percent H PO 3.06 g. (0.024mole) of powdered Te metal, 10 ml. of 30 percent H 0 and 650 ml. ofwater. Solution was complete within 14 hours and 34.8 g. (0.144 mole) ofcopper nitrate was added. The aqueous solution was evaporated over 366g. (436 cc.) of 4-6 mesh CMM Carborundum and fired at 1000 F. Thecatalyst weighed 410 g., calculated at 10.7 percent CU9T61 5PMO1205[) 5On pOrOuS In general, simple catalyst compositions are-preferred, sinceintroduction of another reagent of any kind can bring about substantialchanges in catalyst character, often detrimental. However, it has beenfound that inclusion of a modifying proportion of tin oxide in thecomposition may greatly increase the isobutylene conversion without lossof selectivity, thus alleviating a problem which arises when impureisobutylene is employed as raw material in the form of a mixtureofbutanes and butenes.

A solution containing 75 ml. of water, 17.4 g. (0.072 mole) of coppernitrate trihydrate, 0.008 mole equivalent of tellurophosphomolybdate (1%Te- 1.1P" 12Mo 0 and 0.004 mole (1.00 g.) dibutyltin oxide (dissolved indilute HNO was added to 411 g. of 4-6 mesh CMM Carborundum. Afterfiringin the usual manner, the

and pipes or appear in the aqueous mixture obtained upon isobutylene andoxygen are consumed by this side reaction. It has been disclosed in US.Ser. No. 247,267, US. Ser. No. 247,268 and US. Ser. No. 247,307 that upto about 95 percent of the copper in the catalyst may be replaced bychromium, cobalt or nickel to yield catalysts which may be used withsubstantial reduction of tar formation. These catalysts, being morecomplex, are somewhat more expensive to manufacture but the extraexpense is justified if the cost of isobutylene feed should increase, orif isobutylene should happen to become a scarce commodity. Preferredcatalyst compositions are made by reacting the metallic oxides inapproximately th following proportions:

Following is exemplified the preparation and use of a catalyst in whicha portion of the copper is replaced by chromium.

A copper chromium tellurium phosphorus molybdenum-oxygen catalyst isprepared employing a 4 to 8 mesh size silicon carbide aggregate supportand the following reactants: an aqueous solution of 7.25 g. of Cu(NO -3HO; 11.5 g. of phosphomolybdic acid; 1.15 g. of telluric acid; 6.0 g. ofCr(NO -9H O; and ml. of water. These reactants are combined and added tothe support at elevated temperature. The addition is carried on in sucha manner that the evaporation of the water of the mixture is very rapid.The resulting dry particles of catalyst are fired in an oven for twohours at 1000 F. The empirical formula of the catalyst complex providedis Cr Cu TePMo O The dried supported catalyst has 6.6 percent by weightof the catalyst complex.

The following results are obtained with the provided catalyst inrepeating the above oxidation procedure and the indicated conditions;(1) 488 C., 3.3 seconds contact time, and a ratio by volume(isobutylene/air/H O) of 10.2/70.6/19.2 to provide a 65 percentconversion of isobutylene and yield percentages as follows:methacrolein-J4; COS; and CO 12 (total accountability-94); (2) 475 C.,3.5 seconds contact time, and a ratio of 10.2/70.6/19.2 to provide anisobutylene conversion of 55 percent and a methacrolein yield of 76percent; and (3) 488 C., 3.9 seconds contact time, and a ratio of10.0/68.3/2l.7 to provide an isobutylene conversion of 61 percent andyield percentages as follows: methacrolein75; CO6; and CO 14 (totalaccountability95 There is exemplified below the preparation and use of acatalyst in which a portion of the copper is replaced by cobalt.

A hot mixture of 7.3 g. of Cu(NO -3H O, 8.7 g. of cobalt nitratehexahydrate, 11.6 g. of phosphomolybdic acid, and 1.0 g. of telluricacid in 100 ml. of water is added with stirring to 213 g. of a poroussilicon carbide aggregate having a 4 to 8 mesh size. The addition iscarried on in such a manner that the evaporation of the water of themixture is very rapid. The resulting dry particles of catalyst are firedin an oven for two hours at 1000 F. The dried catalyst is obtained in ayield of 228 g. and has about 6.6 percent by weight of the catalystcomplex of the following formula: Cu co TePMo O (empirical formuladetermined by calculation).

A portion of the catalyst (200 ml.) is placed into a 300-ml. oxidationreactor. A gaseous feed stream of isobutylene is employed having thefollowing composi ion by volume: isobutylene-12.4 percent; air-72.3percent; and water-l5.3 percent. The reaction is conducted atapproximately atmospheric pressure employing a temperature of 495 C. Thecontact time of the gaseous feed with the catalyst bed is an average of2.2 seconds. The product is recovered in the customary manner employingWater scrubbers and is analyzed by the Orsat and GLC methods (as usedherein, GLC means gas liquid chromatography). The conversion ofisobutylene is 48 percent and yields are as follows: methacrolein67percent; CO- percent; and CO 12 percent (total accountabilitypercentage84 percent).

The process is repeated employing a 463 C. reaction temperature, anaverage contact time of 2.0 seconds, and a reaction feed having a ratioby volume (isobutylene/air/ H O) of 12.3/74.1/l3.6 to provide a 31percent conversion of isobutylene and the yield percentages as follows:

methacrolein-73; CO4; and CO -l0 (total accountability84).

The modification of the catalyst by substituting nickel for a part ofthe copper is illustrated below.

A copper-nickel-tellurium-phosphorus-molybdenum catalyst complex isprepared employing silicon carbide aggregate support and the followingreactants: 7.3 g. of Cu(NO 3H O, 11.5 g. of phosphomolybdic acid, 1.15g. of telluric acid. and 3.4 g. of nickel nitrate hexahydrate in 75 ml.of H 0. The reactants, in the form of a hOt aqueous solution, are addedwith stirring to 184 g. of a porous silicon carbide aggregate having a 4to 8 mesh size. The addition is carried on in such a manner that theevaporation of the water of the mixture is very rapid. The resulting dryparticles of catalyst are fired in an oven for two hours at 1000 F. Thedried supported catalys has 6.1 percent by weight of the catalystcomplex. The empirical formula of the complex: Cu -,Ni TePMo O Thefollowing results are obtained with the provided catalyst in repeatingthe above process at the indicated conditions: (1) 484 C., 3.5 secondscontact time, and a ratio by volume (isobutyIene/air/H O) of 10.1/7l.0/19.0 to provide a 56 percent conversion of isobutylene and the yieldpercentages as follows: methacrolein-79; CO 5; and CO l0 (totalaccountability94). (2) 477 C., 3.6 seconds contact time and a ratio byvolume (isobutylene/air/H O) of l0.l/71.0/19.0 to provide a 50 percentconversion of isobutylene and the yield percentages as follows:methacrolein82; CO5; and CO 9 (total accountability-96). (3) 500 C., 4.3seconds contact time and a ratio by volume (isobutyIene/air/H O) ofl0.9/79.4/9.7 to provide a percent conversion of isobutylene and theyield percentages as follows: methacrolein77; CO-6 and CO 12 (totalaccountability (3) Catalyst regeneration The procedure for catalystregeneration is remarkable for its simplicity.

A 175 cc. (158 g.) portion of a catalyst which had been used 2100 hoursand which showed low activity and selectivity was screened to removeapproximately 10 percent of the active catalyst component present asloose, non-adherent powder. The spent catalyst was then treated with asolution of catalyst reagents in the same manner as fresh uncoatedcatalyst support and fired. The new coating was equivalent to 5.7percent Cu Te PMo O on Carborundum CMC. Testing of a cc. charge of therccoated catalyst in a reactor indicated the catalyst to be essentiallyidentical to the original fresh catalyst.

(4) Construction of catalyst bed The catalyst bed is preferablystationary and so positioned that reactants fiow downward verticallythrough the bed. Free space in the reactant entry zone is to be avoided,because of the possible occurrence of non-catalytic gas phase oxidation.Voids in the reactor are preferably packed with particles of inertrefractory material so as to discourage free space reactions.

(B) REACTION CONDITIONS (1) Reactant ratios The hydrocarbon feed streammay contain from about 8 percent isobutylene to substantially pureisobutylene in operation of the process.

The complete reactor feed consists preferabl of preheated hydrocarbon,steam and air, which are introduced into the reaction with prior mixing.It is recommended that approximately the following molar ratios ofreactants be maintained in the feed streams: 1 mole isobutylene/ 1.5moles 0 /1 to 15 moles H 0, preferably about 1.5 moles. The presence ofsteam prevents erratic behavior of the system. The concentrations ofboth isobutylene and oxygen in the gaseous stream through the reactordiminish as the reaction proceeds, resulting in a decrease in reactionrate. It may be desirable to take steps to compensate for this effect soas to obtain the best possible conversion. Otherwise, unreactedisobutylene may be recovered and recycled.

( 2) Temperature Although the operable temperature range is very broad,for economical operation it is recommended that the temperature be keptwithin the range of about 350 to 525 C. Preferably, the temperature isonly permitted to vary between about 430 and 480 C., with the controlpoint set at about 440 C. With adequate provision for heat exchange,continuous cooling will be employed during operation and fluctuation oftemperature will be infrequent. Erratic and violent temperaturefluctuations are not characteristic of the process and may be taken asan indication of failure to maintain the steam feed ratio, or perhaps ofexcessive feeding of oxygen to the system.

(3 Pressure Preferred pressure is one atmosphere plus sufiicientadditional pressure to overcome the resistance of the porous catalystbed to gas flow. The catalyst bed should offer as little resistance togas flow as is practically feasible, so as to create the minimumpressure difierential in the system.

(4) Throughput rate Throughput rate may vary greatly, one volume of feedgas per volume of catalyst bed every 1- to 15 seconds being reasonable.A preferred range is one volume of feed gas per volume of catalyst bedevery 2.5 to 3 seconds. At high linear velocities of gas fiow throughthe catalyst bed, better rates of production of methacrolein per hourper volume of catalyst bed can be obtained but the contact time is shortand control of this condition becomes more critical. Since the obtainingof the higher production rate is accompanied by this need for moreaccurate control, some may choose to operate at lower throughput rates,Where there are fewer control problems.

(C) RECOVERY OF PRODUCT The product may be recovered by conventionalmeans, that is, a water quench of the hot gases, followed by scrubbing,distillation and other steps, including recovery of unreactedisobutylene and other hydrocarbons. Unreacted propylene, if present,should be removed and not recycled, since propylene is oxidized only toa negligible extent in the process and will accumulate in the recyclestream it not eliminated.

The oxidation of isobutylene without substantial effect on propylene, ifpresent, is clear evidence of the specific nature of the combination ofcatalyst and reaction condi- 5 tions in the process as disclosed.

What is claimed is:

1. A method of manufacturing a supported catalyst composition consistingessentially of an intimate mixture of oxides of copper, molybdenum andtellurium comprising: coating an aqueous solution of water-solublecompounds of copper, tellurium and molybdenum as phosphomolybdate orsilicomolyb-date on a refractory solid which is essentially non-reactivewith respect to the metal oxide composition and possesses a surface areaof less than about 10 square meters per gram, evaporating water,decomposing the dry water-soluble compounds by heating to yield acoating on the refractory solid of an intimate mixture of oxides inwhich there are present about 1 to 20 moles of copper oxide and from0.01 to 10 moles of tellurium oxide per 12 moles of molybdenum oxide andheating the intimate mixture of metal oxides so obtained to at least 350C.

2. A supported metal oxide catalyst composition produced by the methodof claim 1 in which the refractory solid is silicon carbide.

References Cited UNITED STATES PATENTS 3,192,259 6/1965 Fetterly et a1252437X 3,243,385 3/1966 Sennewald et al 252437 3,401,197 9/1968 Eden260604X 3,417,128 12/1968 Eden 252437X 3,429,930 2/ 1969 Heslan 252437X3,440,180 4/1969 Kitf et al. 252439 3,446,753 5/1969 Cahoy et al 252439X3,493,608 2/ 1970 Eden 252437X PATRICK P. GARVIN, Primary Examiner US.Cl. X.R. 252439

